Kinematics of Throwing in Paralympic Boccia Athletes with Cerebral Palsy

Abstract

Individuals with cerebral palsy (CP) contend with a number of sensory and motor deficits as a consequence of their neurological impairment. Research on children with CP performing simple tasks of everyday living, such as grasping, reaching, and pointing has commonly identified deficits in spatio-temporal control of the distal joints. A multiple case study design was used to examine the coordination profiles of four skilled Paralympic athletes in the precision throwing sport of Boccia. Three participants with spastic quadriplegia (Boccia Classification Two, BC2, n = 2; and One, BC1, n = 1) and one with ataxic quadriplegia (BC2), performed a total of 80 randomised throws from a wheelchair at a target ball placed at four distances (3 m, 5 m, 7 m, and 9 m) using two sport specific shot types that primarily emphasised either accuracy or speed. A Vicon motion analysis system operating at 200Hz recorded head, trunk, and upper limb joint kinematics which were then analysed using a semi-quantitative and qualitative graphical approach. All participants showed very little spatial variance in hand trajectories and ball release point, with co-compensation of release speed and angle in three participants. Variability in joint kinematics was comparable with research on healthy individuals performing throwing tasks, with distal joints showing greater variability than proximal joints. Increasing target distances and throwing speeds facilitated more independent coupling of the wrist with the shoulder. Angle-angle graphs showed distinctive individual strategies in joint coordination, with all participants modifying joint ranges of motion and velocities under one global movement pattern to changes in target distance, particularly under the accuracy-emphasised constraint. No significant differences in kinematics existed between successful and unsuccessful shots. The findings are consistent with existing literature on precision throwing and in support of the notion of compensatory variability in goal-directed human movement. In a complex multi-joint movement, individuals with cerebral palsy can move with high levels of precision and functionality.